The confusion, among christians, as well as in the society at large about what the separation of religion from politics and the increasing accummulation of power by the state needs to be untangled. The theologian William Cavanaugh has done some great work in challenging the received wisdom on this issue.
The story of separation of "religion" and “politics” in Europe and the development of the “secular” state, as normally narrated, begins with the wars of religion triggered by the Reformation. A state free from "religious" control was necessary to ensure tolerance and suppress the violence of competing religious forces. This narration gains plausibility against the background of the co-option of the Christian church by the Roman Empire, the emergence of Christendom and the use of imperial violence to enforce conversion to the Christian faith. According to William Cavanaugh (“A Fire Strong Enough to Consume the House – The Wars of Religion and the Rise of the State” Modern Theology, 1995)
"The "Wars of Religion" were not the events which necessitated the birth of the modern State; they were in fact themselves the birthpangs of the State. These wars were not simply a matter of conflict between "Protestantism" and "Catholicism," but were fought largely for the aggrandizement of the emerging State over the decaying remnants of the medieval ecclesial order. … behind these wars is the creation of "religion" as a set of beliefs which is defined as personal conviction and which can exist separately from one's public loyalty to the State. The creation of religion, and thus the privatization of the Church, is correlative to the rise of the State. "
As a result we have the invention of “religion” as a sphere of life, a realm of individual choice and private concern disconnected from public, community and social life is intertwined with the emergence of the state as "sovereign", with a total monopoly of power within a limited geographic area. In another article Canavanugh argues that
"… the term "religion" has accompanied the domestication of Christianity. It has facilitated the marginalisation of the radical claims of the gospel and the transfer of the Christian's ultimate loyalty to the supposedly rational spheres of nation and the market. The church is now a leisure activity: the state and the market are the only things worth dying for. The modern concept of religion facilitates idolatry, the replacement of the living God with Caesar and Mammon. " ("God is not Religious")